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Full text of "Handbook Of Chemical Engineering - I"

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3.  Bone (interlaminated coal and slate), usually flat and either coal-faced or slate-faced.
4.  Flat slate from 0.25 to 0.5 in. thick.
5.  Pure slate with coal faces, approximately cubical in form.
6.  Slate and rock, heavy, and cubical in form.
Of these classes (2) and (5) cannot be separated by a fractional separating device. In separating by specific gravity fairly good results are obtained in separating groups (2) and (5) but in using jigs, the most common sort of gravitational separation device, much glassy fractured coal, class (1) goes over into the slate discharges with classes
FIG. 3.—Separation by friction.
(5) and (6). The point these observations bring out are that none of the separation devices for coal are perfect and that even to get good commercial results additional separation means must be used. In the case of the separator under discussion the work performed is of a roughing character and the inventor advocates hand separation or jigging or both following its use.
Figure 3 shows the general arrangement of the machine. The traveling separating belt is mounted on two shafts and the direction of travel of the belt is upward towards the material receiving side. The traveling belt is inclined forward as well as downward in the direction of travel. The material is fed in a continuous stream at the farther left-hand corner and as it slides off the feeding pan it is immediately spread out on the separating belt. The coal slides down until it comes in contact with the guide at the lower end and then works its way along the guide to the discharge point at the lower right-hand corner. The slate is carried up and discharges at the upper end.
The capacity of the machine ranges from 5 tons an hour on pea size (through 0.75-in. and over a 0.5-in. screen) to 25 tons an hour for steamboat size (through a 6-in. and over a 4.5-in. screen). On steamboat size four of these separators and 12 men do the work that 32 men do by hand sorting.
For separating coal from narrow seams the complete process of separation would involve an arrangement as follows: First the use of the Ay res separators which will divert from 60 to 75 per cent of the total pure coal when properly adjusted. The impure product is run over a second set of separators to remove all the flat slate, class (4) and all pure slate and rock, group (6). The reject from the second set of